Method for authorising locking and/or starting a motor vehicle and associated device

ABSTRACT

The disclosure relates to a method for identifying and authorizing unlocking or starting of a motor vehicle for a hands-free access system, comprising a central unit (C) exchanging identification messages with identification units (B 1,  B 2,  B 3 ) according to a communication procedure, said procedure including:  
     a step that consists in emitting an identification message (CH) from the central unit (C) to the identification units (B 1,  B 2,  B 3 );  
     a step that consists in emitting a message indicating the presence (ANTI) of said identification units (B 1,  B 2,  B 3 ) having received the identification message (CH) to the central unit (C);  
     a step that consists in emitting a selection message (SEL) by the central unit (C) to select one particular identification unit (B 3 ) to reply to the identification message;  
     wherein the procedure includes a step that consists in emitting an additional identification message (CH 2 ), and wherein said step of sending a presence indication message (ANTI) and/or said step of sending a selection message (SEL) is performed between said step of sending an identification message (CH) and said step of sending the additional identification message (CH 2 ) so as to enhance the security of interchange between said central unit (C) and said identification units. The invention also concerns a device for identifying and authorization unlocking and/or starting of a motor vehicle.

[0001] The invention concerns a method for identifying and authorizing unlocking and/or starting of a motor vehicle, for a so-called hands-free motor vehicle access system, and an associated identification and authorization device.

[0002] Such an access system is represented schematically in FIG. 4. It comprises a central unit C, mounted in the vehicle, which exchanges identification data with identification units B1, B2, B3. Each identification unit, often referred to as a badge, is generally carried by a user. When the central unit C recognizes a badge, it authorizes unlocking or starting of the vehicle.

[0003] In order to better appreciate the invention, it is helpful to present a known communication procedure and its disadvantages.

[0004]FIG. 1 shows the communication diagram of a central unit C of such a system along with the communication diagrams of the badges B1, B2, B3 dialoging with this unit.

[0005] After a pre-defined triggering action, for example a user approaching a handle of the vehicle, the central unit C of the access system switches to transmit mode and sends a so-called wake-up (WU) message.

[0006] If a user carrying a badge B1 is near the vehicle, the badge detects this wake-up message and switches to listening mode.

[0007] The central unit then emits an coded identification message CH, then chooses the badge with which it will communicate to avoid several badges simultaneously sending a response. This step of the communication protocol comprises two phases generally called the anti-collision phase ANTI and the selection phase SEL.

[0008] During the anti-collision phase ANTI, badges present around the vehicle emit a message indicating their presence. In the example shown in FIG. 1, badges B1, B3 located near the vehicle each send a pulse A1, A3 indicating their presence.

[0009] During the selection phase SEL, the central unit selects a badge by sending a pulse SEL1 characteristic of the badge B1 it has chosen. The other badge B3 then puts itself in standby mode.

[0010] The central unit then emits synchronization pulses S1, S2, S3 at regular time intervals T. On reception of each synchronization pulse, the selected badge B1 emits a coded response pulse IR1 which is a part of the response message REP. The synchronization pulses S1, S2, S3 enable the processing time of the badge to be measured. This time measurement, usually called the anti-pirate stage, enables the unlocking to be inhibited when malevolent people equipped with pirate transmit/receive units attempt to steal the vehicle. In effect, when pirate transmit/receive units are interposed between the badge and the vehicle, the central unit receives the pulse of the response message IR1 after a time longer than the processing time of the badge T owing to the delay introduced by the processing time of the pirate units.

[0011] However, the security of a communication procedure of this type is insufficient, since we could imagine that the pirate units mask the delay that they introduce by eliminating the anti-collision ANTI and selection SEL phases. In particular, pirates can trigger the communication procedure, and, after amplification, send to the badge the wake-up WU and identification CH messages. Next they interrupt the communication with the central unit and generate synchronization pulses. They receive the response pulses generated by the badge and return them to the central unit, at the right moment. Consequently, the central unit cannot detect the presence of the pirate units, and the security of the vehicle access system is compromised.

[0012] One object of the present invention is an identification procedure offering a higher level of security.

[0013] To this end, the invention proposes a method for identifying and authorizing unlocking or starting of a motor vehicle for a hands-free access system, comprising a central unit exchanging identification messages with identification units according to a communication procedure, said procedure including:

[0014] a step that consists in emitting an identification message from the central unit to the identification units;

[0015] a step that consists in emitting a message indicating the presence of said identification units having received the identification message to the central unit;

[0016] a step that consists in emitting a selection message by the central unit to select one particular identification unit to reply to the identification message;

[0017] wherein the procedure includes a step that consists in emitting an additional identification message, and wherein said step of sending a presence indication message and/or said step of sending a selection message is performed between said step of sending an identification message and said step of sending the additional identification message so as to enhance the security of interchange between said central unit and said identification units.

[0018] In this manner, the step of sending the additional identification message is immediately followed by the step of reception of the response message such that a delay introduced after the step of emission of the additional identification message is always detected by the central unit.

[0019] The procedure according to the invention can also include one or more of the following characteristics:

[0020] the additional identification message depends on the identification message to enhance the security of the communication procedure;

[0021] the central unit is able to calculate part of the response message as soon as the identification message is received to reduce the duration of the communication procedure;

[0022] the identification message is a random number generated by the central unit;

[0023] the procedure also includes:

[0024] a step that consists in emitting synchronization pulses from the central unit to the particular identification unit;

[0025] a step that consists in emitting a response message from the particular identification unit to the central unit, this response message comprising at least two response pulses, the response pulses being emitted by the identification unit only after reception of the synchronization pulses so as to measure the processing time of the identification unit, the synchronization pulses being coded so as to contain the additional identification message to reduce the duration of the communication procedure;

[0026] the synchronization pulses are coded by modulation of their positions

[0027] the synchronization pulses are coded by modulation of their widths

[0028] These characteristics also enable the duration of the communication procedure to be advantageously reduced, so that the user only has to wait a few seconds before the vehicle door opens, which increases the comfort of use.

[0029] The present invention also includes an identification and authorization device or a motor vehicle starting device offering a high level of security.

[0030] To this end, the invention proposes a device for identifying and authorization unlocking or starting of a motor vehicle comprising a central unit exchanging identification messages with identification units according to a communication procedure, said central unit being able to send an identification message to said identification units and a selection message to a particular identification unit, said identification units each being able to send a message indicating their presence, wherein said device is able to send an additional identification message and wherein said message indicating presence and/or said selection message is sent after sending said identification message and before sending said additional identification message so as to enhance the security of the interchange between said central unit and said identification units.

[0031] Advantageously, the central unit emits synchronization pulses to the particular identification unit which emits response pulses on receiving the synchronization pulses, which enables the processing time of the particular identification unit to be measured. The synchronization pulses are coded so as to contain the additional identification message to reduce the duration of the communication procedure.

[0032] The invention will be better understood on reading the detailed description below of an embodiment, which is non-limitative and taken only as an example, with reference to the attached drawings of which:

[0033]FIG. 1 is a diagram of a communication protocol according to the prior art, already described in the introductory part of the description,

[0034]FIG. 2 is a diagram of the communication protocol between a computer and identification units according to the single embodiment of the present invention,

[0035]FIG. 3 is a diagram of a part of the communication protocol according to a possible enhancement of the single embodiment of the present invention,

[0036]FIG. 4 illustrates a hands-free access system.

[0037] The steps of the communication procedure according to the invention that are identical to steps of the prior art procedure carry the same references.

[0038] According to the invention, the communication procedure includes an additional identification message CH2.

[0039] As seen in FIG. 2, this message is immediately followed by the step of reception of the response message REP. Consequently, if pirate units are interposed between the badge B3 previously selected and the central unit C, the pulses of the response message IR1 are necessarily received with a delay corresponding to the processing time of the pirate units. In this manner the communication procedure according to the invention provides a higher level of security than a classic communication procedure.

[0040] In effect, since the sending of the additional identification message CH2 is directly followed by sending of the response message REP, no part of the communication procedure can be eliminated to mask the delay introduced by the pirate units.

[0041] Obviously the additional identification message CH2 is necessary to give the authorization to send the response message such that it can not be truncated.

[0042] It can, for example, contain a function of the encryption key indispensable to calculate the response message.

[0043] Advantageously, the additional identification message CH2 also contains a coded function of the identification message CH so as to increase, by encryption, the security of the communication between the badge and the vehicle's computer.

[0044] The identification message CH is either a random number generated by the central unit C, or a pre-registered number.

[0045] Advantageously, the identification message CH is emitted before the anti-collision ANTI and selection SE phases. In this manner, the microcontroller of the badge pre-computes the response message REP during the anti-collision and selection phases such that after reception of the additional identification message (CH2), the response message is computed faster, which therefore reduces the duration of the communication procedure.

[0046]FIG. 3 represents schematically part of a communication diagram between the central unit C and a badge B1 selected according to an enhancement of the present invention.

[0047] This enhancement enables the length of the communication procedure to be reduced and consequently it improves significantly the usability of a hands-free access system.

[0048] According to this enhancement, the synchronization pulses S1, S2, S3 are coded so as to contain an identification message. In this way, the additional identification message CH2 can, for example, be transmitted simultaneously with the synchronization. The coding can be performed by modulation according to the width or position of the synchronization pulses.

[0049] In the embodiment of the present invention shown in FIG. 3, the synchronization and identification data are contained in the emitted pairs of pulses S1, S1′, S2, S2′, S3, S3′. A pair of pulses is constituted by a first pulse S1 and a second pulse S2. The first pulses S1, S2, S3 are always emitted at a constant time interval T. They thereby form the synchronization of the signal. The second pulses S1′, S2′, S3′ contain the additional identification message CH2.

[0050] For example, according to FIG. 3, the pulses S1′ and S3′ emitted after a time t1 defined relative to the emission of the first pulses S1 and S3, code a data item corresponding to 1. The pulse S2′ emitted after a pre-defined time t0 defined relative to the emission of the first pulse S2, codes a data item corresponding to 0.

[0051] After reception of a pair of pulses S1, S1′, the badge emits a pulse of the response message IR1 during the period T. If the central unit receives no reply during time T, the central unit stops the communication procedure. In this manner the anti-pirate function is always executed.

[0052] As in a classic communication procedure, the response pulses IR1, IR2 are coded. We can for example choose to send a pulse IR1 to code a data item equal to 1 but not send a pulse IR2 to code a data item equal to 0. The coding can also be performed by means of the pulse width or a modulation of their positions.

[0053] According to an advantageous variant, the same antenna is used to receive and transmit messages. This antenna is connected via a switch to a transmit amplifier stage and to a receive amplifier stage. A microcontroller controls the switching frequency of this switch. The patent application number FR 2 794 603 filed by the applicant of the present invention describes a bidirectional transmission system of this type.

[0054] If a single antenna is used, the communication procedure of badge B1 and the computer C include alternating emission steps Tx and reception steps Rx of the data, of the same period but with opposite phase.

[0055] As seen in FIG. 3, after reception of a pair of pulses, the badge switches to transmit mode Tx and emits a response pulse. Simultaneously, the central unit switches to receive mode Rx. The communication procedure therefore enables bit-by-bit interchange of the data at the same frequency, for example (in the case of radio frequency) at 315, 434 or 868 MHz.

[0056] The first pulses S1, S2, always provide the synchronization function, since the badge needs this synchronization to start its reception phase at a regular time interval and to obtain a precise measurement of the distance between the badge and the central unit. Thanks to this synchronization, the communication procedure is faster and more efficient.

[0057] Obviously the badge and the central unit could each have two antennas, in which case one antenna is dedicated to message emissions and the other to message receptions. 

1. Method for identifying and authorizing unlocking or starting of a motor vehicle for a hands-free access system, comprising a central unit (C) exchanging identification messages with identification units (B1, B2, B3) according to a communication procedure, said procedure including: a step that consists in emitting an identification message (CH) from the central unit (C) to the identification units (B1, B2, B3); a step that consists in emitting a message indicating the presence (ANTI) of said identification units (B1, B2, B3) having received the identification message (CH) to the central unit (C); a step that consists in emitting a selection message (SEL) by the central unit (C) to select one particular identification unit (B3) to reply to the identification message; wherein the procedure includes a step that consists in emitting an additional identification message (CH2), and wherein said step of sending a presence indication message (ANTI) and/or said step of sending a selection message (SEL) is performed between said step of sending an identification message (CH) and said step of sending the additional identification message (CH2) so as to enhance the security of interchange between said central unit (C) and said identification units.
 2. Procedure according to claim 1 wherein said additional identification message (CH2) depends on said identification message (CH) to enhance the security of the communication procedure.
 3. Procedure according to one of claims 1 to 2, wherein said central unit (C) computes the response message (REP) on reception of said identification message (CH) to reduce the duration of the communication procedure.
 4. Procedure according to one of claims 1 to 3, wherein said identification message (CH) is a random number generated by said central unit (C).
 5. Procedure according to one of claims 1 to 4 also including: a step that consists in emitting synchronization pulses (S1, S2) from said central unit (C) to said particular identification unit (B3); a step that consists in emitting a response message (REP) from said particular identification unit (B3) to said central unit (C), this response message (REP) comprising at least two response pulses (IR1, IR2), the response pulses (IR1, IR2) being) emitted by said identification unit only after reception of the synchronization pulses (S1, S2) so as to measure the processing time of the identification unit, wherein said synchronization pulses (S1, S2) are coded so as to contain said additional identification message (CH2) to reduce the duration of the communication procedure.
 6. Procedure according to claim 5, wherein said synchronization pulses are coded by modulation of their positions.
 7. Procedure according to claim 5, wherein said synchronization pulses are coded by modulation of their widths.
 8. Device for identifying and authorization unlocking or starting of a motor vehicle comprising a central unit (C) exchanging identification messages with identification units according to a communication procedure, said central unit (C) being able to send an identification message (CH) to said identification units and a selection message (SEL) to a particular identification unit (B3), said identification units (B1, B2, B3) each being able to send a message indicating their presence (ANTI), wherein said device is able to send an additional identification message (CH2) and wherein said message indicating presence (ANTI) and/or said selection message (SEL) is sent after sending said identification message (CH) and before sending said additional identification message (CH2) so as to enhance the security of the interchange between said central unit (CC) and said identification units.
 9. Device according to claim 8, wherein said central unit (CC) emits synchronization pulses (S1, S2) to said particular identification unit (B3) and wherein said particular identification unit (B3) emits response pulses (IR1, IR2) after reception of said synchronization pulses (S1, S2) to measure the processing time of said particular identification unit (B3), and wherein said synchronization pulses (S1, S2) are coded so as to contain said additional identification message to reduce the duration of said communication procedure. 